Unsaturated polyester compositions are useful in the manufacture of shaped articles such as bathroom fixtures, boats, automotive parts and the like. In most of these applications it is necessary to color the polyester compositions by incorporating a color-imparting amount of a material that imparts color to the polyester compositions. A typical polyester colorant is disclosed in U.S. Pat. Nos. 4,250,078 (McFarlane et al.) and 4,420,581 (McFarlane et al.). These patents disclose the use of iron oxides to impart color to polyester compositions. The iron oxides may be used in combination with certain anthraquinone dyes which are copolymerized into the polyester compositions. While the coloring of polyester with iron oxide or iron oxide/dye combinations has been effective it is not without its shortcomings. First of all, the production of colored polyester using anthraquinone dyes as colorants is quite costly. Secondly, the iron oxide colorants have a tendency to cloud the polyester compositions. Clouding is often undesirable since many of these polyester compositions are used in applications wherein the polyester must be clear enough not to obstruct vision. Lastly, iron oxide colorants have a tendency to be unevenly distributed throughout the polyester compositions thereby resulting in non-uniform coloring of the polyester. This non-uniformity results from the difficulty in evenly distributing the iron oxide colorants during the bleeding step that usually precedes molding or casting operations.
Accordingly, it is the primary object of the present invention to provide an alternative colorant for use in polyester compositions.
It is a further object of the present invention to provide an inexpensive colorant for polyester compositions which enables production of colored polyesters of greater clarity than previously available.
It is a still further object of the present invention to provide a colorant which may be added during the polymerization of the polyesters to thereby eliminate the colorant blending step and also achieve greater color uniformity in the polyester.
These and other objects of the present invention will be apparent to one of ordinary skill in the art from the summary and detailed description which follow.